Adjuvant therapy for resectable breast cancer

Development of malignant breast microcalcifications after neoadjuvant chemotherapy in advanced breast cancer

The increased interest in the use of neoadjuvant chemotherapy for patients with locally advanced or large tumors at initial presentation necessitates the recognition of sequelae of this therapy. This article describes the interval appearance of malignant, linear-branching, microcalcifications during neoadjuvant chemotherapy for locally advanced breast cancer. Mammographically the malignant microcalcifications appeared only in the region of the breast where the primary tumor was found. Pathologically only a subpopulation of malignant cells responded to the chemotherapy, demonstrating viability of the majority of the tumor, with cell death only in the subpopulation. With the increased use of neoadjuvant chemotherapy, it is important to recognize previously undescribed mammographic findings secondary to this therapeutic approach.

Development and validation of a patient-specific predictive instrument for the need for dose reduction in chemotherapy for breast cancer: a potential decision aid for the use of myeloid growth factors

A predictive instrument for chemotherapy dose reductions would help optimize delivery of planned chemotherapy and rationalize the use of myeloid growth factors. We analyzed data on 833 women with breast cancer treated with cyclophosphamide, doxorubicin, and fluorouracil, for six cycles in two phase III clinical trials. From the first study ( n=323), we generated a logistic regression model that predicts an individual patient's probability of receiving significantly reduced chemotherapy, defined as less than 85% of the planned dose over cycles 2-6, using data generated from cycle 1. The model was validated on data from the second study ( n=510). The predictive model's variables include nadir absolute neutrophil count (ANC) in cycle 1 (OR: 0.14, 95% CI: 0.06-0.30, P<0.001) and percent drop of platelets between day 1 and the nadir in cycle 1 (OR: 1.04, 95% CI: 1.02-1.05, P<0.001). Both variables are dose adjusted based on the chemotherapy cycle 1 dose. The model's discriminatory performance was good (ROC area=0.82), as was the calibration of predicted with actual frequencies of dose reductions. In the validation dataset, model variables remained significant, with an ROC area of 0.78 and good calibration. In summary, we devised and validated a predictive instrument that uses data from a patient's first cycle of chemotherapy to compute the probability of requiring a significant chemotherapy dose reduction on subsequent cycles. This instrument could help clinicians select patients who will benefit from early administration of myeloid growth factors.

Biodegradable poly(epsilon -caprolactone) nanoparticles for tumor-targeted delivery of tamoxifen

To increase the local concentration of tamoxifen in estrogen receptor (ER) positive breast cancer, we have developed and characterized nanoparticle formulation using poly(epsilon -caprolactone) (PCL). The nanoparticles were prepared by solvent displacement method using acetone-water system. Particle size analysis, scanning electron microscopy, zeta potential measurements, and differential scanning calorimetry (DSC) were used for nanoparticle characterization. Biodegradation studies were performed in the presence and absence of Pseudomonas lipase in phosphate-buffered saline (PBS, pH 7.4) at 37 degrees C. Tamoxifen loading over different concentrations was analyzed by high-performance liquid chromatography (HPLC) and the optimum loading concentration was determined. In vitro release studies were performed in 0.5% (w/v) sodium lauryl sulfate (SLS) containing PBS at 37 degrees C. Cellular uptake and distribution of fluorescent-labeled nanoparticles was examined in MCF-7 breast cancer cells. SEM micrographs and Coulter analysis showed nanoparticles with spherical shape and uniform size distribution (250-300 nm), respectively. Zeta potential analysis revealed a positive surface charge of +25 mV on the tamoxifen-loaded formulation. Being hydrophobic crystalline polyester, PCL did not degrade in PBS alone, but the degradation was enhanced by the presence of lipase. The maximum tamoxifen loading efficiency was 64%. Initial burst release of tamoxifen was observed, probably due to significant surface presence of the drug on the nanoparticles. A large fraction of the administered nanoparticle dose was taken up by MCF-7 cells through non-specific endocytosis. The nanoparticles were found in the perinuclear region after 1 h. Results of the study suggest that nanoparticle formulations of selective ER modulators, like tamoxifen, would provide increased therapeutic benefit by delivering the drug in the vicinity of the ER.

Integrin signaling inhibits paclitaxel-induced apoptosis in breast cancer cells

Inherent or acquired drug resistance is one of the major problems in chemotherapy. The mechanisms by which cancer cells survive and escape the cytotoxic effects of chemotherapeutic agents are essentially unknown. In the present study, we demonstrate that in the MDA-MB-231 and MDA-MB-435 breast cancer cells, ligation of beta1 integrins by their extracellular matrix ligands inhibits significantly apoptosis induced by paclitaxel and vincristine, two microtubule-directed chemotherapeutic agents that are widely used in the therapy of breast cancer. We show that beta1 integrin signaling inhibits drug-induced apoptosis by inhibiting the release of cytochrome c from the mitochondria in response to drug treatment. Further, integrin-mediated protection from drug-induced apoptosis and inhibition of cytochrome c release are dependent on the activation of the PI 3-kinase/Akt pathway. Our results identify beta1 integrin signaling as an important survival pathway in drug-induced apoptosis in breast cancer cells and suggest that activation of this pathway may contribute to the generation of drug resistance.